The hostname to send logs to. This should target the loggly http input
server which is usually "logs-01.loggly.com" (Gen2 account).
See Loggly HTTP endpoint documentation at
https://www.loggly.com/docs/http-endpoint/

You can use %{foo} field lookups here if you need to pull the api key from
the event. This is mainly aimed at multitenant hosting providers who want
to offer shipping a customer’s logs to that customer’s loggly account.

Retry count.
It may be possible that the request may timeout due to slow Internet connection
if such condition appears, retry_count helps in retrying request for multiple times
It will try to submit request until retry_count and then halt